In an optical communication system, an optical transmitter can convert electrical signals that are modulated with information into optical signals for transmission via an optical fiber. An opto-electronic light source, such as a laser, performs the electrical-to-optical signal conversion in an optical transmitter. An optical receiver can receive the optical signals via the optical fiber and recover the information by demodulating the optical signals. An opto-electronic light detector, such as a photodiode, performs the optical-to-electrical signal conversion in an optical receiver. In addition to light sources and light detectors, opto-electronic transmitters and receivers commonly include lenses, reflectors and other optical elements, mechanical structures for retaining such elements, and optical and electrical interconnections.
Optical transmitters and receivers can be modularized. As illustrated in FIG. 1, an optical transceiver module 10 can includes a housing 12 in which the above-described opto-electronic and optical elements are retained. In a forward end of housing 12, a multiple-fiber push-on (MPO) connector 14 retains the ends of a number of parallel optical fibers 16. Although not shown in FIG. 1 for purposes of clarity, the other ends of fibers 16 are coupled to optical or opto-electronic elements within housing 12. A mating connector 18 can be plugged into optical transceiver module 10. When mating connector 18 is plugged into optical transceiver module 10 (indicated by the arrows), mating connector 18 is not only mechanically connected or mated with transceiver module 10 but the ends of optical fibers 16 are also optically coupled with the ends of optical fibers 20 of mating connector 18.
To promote secure mechanical connection between mating connector 18 and optical transceiver module 10, MPO connector 14 has two substantially cylindrical pins 22 that engage correspondingly shaped bores (not shown) in mating connector 18. As further illustrated in FIG. 2A, each of pins 22 has an elongated shaft 24 and a groove 26. To assemble pins 22 with MPO connector 14, pins 22 are inserted into bores (not shown) in MPO connector 14, and a retaining plate 30 is snapped into grooves 26 in the manner illustrated in FIGS. 3-4. (MPO connector 14 is not shown in FIGS. 3-4 for purposes of clarity.) Referring again to FIG. 1, when pins 22 are assembled with MPO connector 14 in this manner, retaining plate 30 abuts the rearward wall of MPO connector 14. To facilitate the snapping action, grooves 26 have a trough-shaped or curving contour, the retaining plate may have a relief along the sides of the slots to capture the pin (not shown), and both retaining plate 30 and grooves 26 must be made to close tolerances. If mating dimensions are looser, it may be easier to snap retaining plate 30 into grooves 26, but retaining plate 30 may not retain pins 22 as securely. If mating dimensions are tighter, retaining plate 30 may hold pins 22 more securely, but it may be more difficult to snap retaining plate 30 into grooves 26.
The assembled MPO connector 14 is mounted in housing 12 in an orientation in which the ends of pins 22 abut an interior wall 28 of housing 12. Retaining plate 30 inhibits pins 22 from being withdrawn from the forward end of MPO connector 14. The abutting arrangement between the ends of pins 22 and wall 28 inhibits pins 22 from being pushed further into housing 12. Nevertheless, if care is not taken when mating connector 18 is plugged into optical transceiver module 10 and unplugged from optical transceiver module 10, it is possible for pins 22 to be dislodged from their positions in MPO connector 14. Also, it is possible that while mating connector 18 and optical transceiver module 10 are connected, a force that is applied to one of mating connector 18 and optical transceiver module 10 can cause what is sometimes referred to in the art as “wiggle,” in which the ends of optical fibers 16 in MPO connector 14 move out of optical alignment with the ends of optical fibers 20 of mating connector 18. Such wiggle results in the optical power coupled through connectors 14 and 18 to fluctuate up and down.
Pin configurations other than that described above are known. For example, as illustrated in FIG. 2B, a pin 32 has an elongated shaft 34 and a head 36. Head 36 has a larger diameter than shaft 34. Head 36 serves a function similar to that of above-described groove 26 by inhibiting pin 32 from being withdrawn from the forward end of an MPO connector.